This invention relates to a device for recording data. More particularly this invention relates to an optical device for recording data related to seismic prospecting operations.
The data collected during such operations are now digitalized as soon as they are received and are recorded on magnetic tapes. In view of the necessity to represent the data in a readable document, there is used a recorder adapted to convert the digitalized data to visible traces and to arrange the traces so as to obtain a complete depth section of a seismic profile.
The transfer of the digitalized information into a visible form may be achieved in two different modes. According to the first mode, the information is transferred onto a paper support by means of a machine of the printing type and is converted to a plotting of variable area where the black portions are formed by the juxtaposition of printed points. However, these printed points have a finite minimum width, thereby limiting the frequency of the curves which can be represented.
According to the second mode, the information is transferred onto a sensitive support. The sensitive support may be, e.g., the screen of an oscilloscope whose beam deviation system is actuated by a control signal responsive to the signals to be recorded.
The sensitive support may also have the form of a support sensitive to light. It is sensitized by a light beam whose motion and/or intensity depends on the signals to be recorded.
A commonly used recording system comprises an element for generating a light beam, elements for imparting to the light beam an oscillatory motion and/or varying its intensity according to the selected type of recording (galvanometric, of variable area, of variable density or a combination thereof), a sensitive support attached to a revolving drum and means to shift the beam with respect to the support. The drum makes one revolution for each recording trace.
The disadvantage of this type of recorder consists essentially in the fact that the maximum number of traces which can be recorded is limited by the width of the sensitive support attached to the drum. When to seismic prospecting operations are conducted on a large scale, it is necessary, in order to represent seismic profiles of great length, to fractionate the optical recordings, the width of each recording depending on the length of the drum generatrix, and then to employ photo-assembly to reconstitute the seismic profile representation to its whole extent.